This invention relates generally to motor vehicle internal combustion engines having electronic governors. More specifically, the invention relates to engines, systems, and methods for compensating a P-I-D (proportional-integral-derivative) engine governor as the engine is warming up to improve engine speed stability, such as when the engine is idling.
A known electronic engine control system in a motor vehicle comprises a processor-based system that processes data from various sources to develop control data for controlling certain functions of the engine. A processor-based control system processes certain data useful in setting a data value for engine fueling representing the quantity of fuel that is to be injected by fuels injectors into engine cylinders where the injected fuel is combusted to run the engine and power the vehicle.
An electronic governor can be incorporated into an electronic engine control system to provide engine governing. The governor develops data represented governed fueling, and that governed fueling data is used to govern the quantity of fuel injected by the fuel injectors for the purpose of limiting engine speed at times when the engine might otherwise seek to run at a higher speed.
An electronic engine governor operates to govern engine fueling according to the particular governor strategy incorporated into the electronic engine control system. Commonly owned U.S. Pat. No. 6,425,370 describes a diesel engine load governor using engine speed setpoint.
A known engine control system that is present in certain engines manufactured by International Truck and Engine Corporation is premised on isochronous speed regulation and utilizes engine speed as a setpoint that is subsequently processed with additional data for developing a proper fueling command to operate the engine at the corresponding speed. The processor contains programmed data correlating engine speed setpoint data with combinations of accelerator pedal position data and engine load data and processes accelerator pedal position data and engine load data in accordance with that programmed data to develop the engine speed setpoint data.
The driver of a motor vehicle that is powered by a diesel engine typically uses an accelerator pedal to accelerate the engine, and the accelerator pedal position data comes from an accelerator position sensor (APS) operated by the accelerator pedal. Actual engine speed is an input to the governor P-I-D, and engine speed error, meaning the difference between actual engine speed and the engine speed setpoint, is another input to the governor P-I-D. The governor P-I-D processes the inputs to develop output data representing a governed mass fuel input to the engine. The engine control system subsequently develops a corresponding pulsewidth signal for operating the engine fuel injectors.
As the engine is warming up, the effect of the governor on engine fueling may at times cause variations in engine idle speed that some may consider undesirably excessive. The driver of a motor vehicle powered by such an engine may consider such variations objectionable, or perhaps even perceive them as a problem with the engine. Although the proportional-integral-derivative (P-I-D) function is typically calibrated for general governing with the engine fully warmed, such a strategy can aid in controlling governor-induced speed variations during warm-up, such as when the engine is idling.
The P-I-D governor function is part of a closed-loop strategy based on engine speed error and control gains. The governed fueling data developed by P-I-D processing comprises a proportional component that processes the engine speed error input, an integral component that processes the engine speed error input, and a derivative component that processes the engine speed error input. The calibration of the governor allows a different control gain to be used in the development of each of the three components. The three components are summed together by a summing function to create the governed fuel data.
It is believed that further reductions in governor-induced speed variations, especially during warm-up of a cold diesel engine would be desirable. It is toward that objective that the present invention is directed.
Accordingly one generic aspect of the invention comprises an internal combustion engine that comprises an electronic engine control system and a fueling system governed by an electronic P-I-D governor in the electronic engine control system. The P-I-D governor provides a data output having a proportional component, an integral component, and a derivative component, each of which is derived from closed-loop processing of engine speed error data. The P-I-D governor further comprises a function that provides a further component to the data output, that further component comprising a data value that is based on engine temperature and on elapsed engine running time since the engine was last started.
Still other generic aspects relate to an engine control system having a governor as just described and the method that is performed.
The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows.